In cast molding methods of producing ophthalmic lenses, such as contact lenses, a reaction mixture or polymerizable lens precursor composition is cured in a lens shaped cavity defined by a first mold member and a second mold member, or a female and male mold member, respectively. The mold members are typically produced by injection molding a thermoplastic material into mold shaped cavities. Examples of thermoplastic materials include non-polar resins, such as polypropylene, polystyrene, and polyethylene; and polar resins, such as ethylene-vinyl alcohol polymeric resins, and polyvinyl alcohol polymeric resins. The first and second mold members are placed or coupled together to form the lens shaped cavity.
One type of coupling of the first mold member and second mold member utilizes an interference fit between the first and second mold members. For example, the second mold member may be held in place relative to the first mold member by a pressure fit provided by a portion of the first mold member acting on a portion of the second mold member. An interference fit can be understood to be a fastening between first and second mold members that is achieved by friction between a portion of the first mold member and a portion of the second mold members after the mold members are pushed or pressed together.
Another type of coupling is referred to as a point contact coupling. With point contact mold members, the first and second mold members are placed in contact with each other, and require an additional coupling mechanism to hold the two mold members together. For example, two point contact mold members can be held together by physically clamping the mold members together using an additional device. Or, two point contact mold members can be held together by fusing a portion of the two mold members together.
The type of coupling used to form the contact lens molds often relates to the type of material used to produce the mold members. For example, more elastic or flexible polymeric materials, such as relatively non-polar or hydrophobic polymeric resins, may be used to form interference fit mold members. In comparison, more rigid or inflexible polymeric materials, such as relatively polar or hydrophilic polymeric materials, may be used to form point contact mold members.
When polypropylene or polystyrene contact lens molds, which are suitable for interference fit coupling, described above, are used to produce silicone hydrogel contact lenses, it is known that the silicone hydrogel contact lenses so produced require surface treatments or an interpenetrating polymer network (IPN) of a polymeric wetting agent in order to make the lenses ophthalmically acceptable or have ophthalmically acceptable surface wettabilities.
Contact lens molds that are made from SOARLITE™ S (a polar resin of ethylene-vinyl alcohol (EVOH) copolymers available from Nippon Gohsei, Ltd.) are effective in producing silicone hydrogel contact lenses having ophthalmically acceptable wettabilities without requiring a surface treatment or an IPN of a polymeric wetting agent to provide the wettability of the silicone hydrogel contact lenses. Due to the rigidity of SOARLITE™ S, the first and second mold members are coupled together using the point contact coupling described above, as opposed to an interference fit coupling.
In view of the above, it can be appreciated that a need exists for new lens molding devices and methods that do not require contact point coupling for the manufacture of ophthalmic lenses, such as silicone hydrogel contact lenses, that are ophthalmically compatible without requiring a surface treatment or a polymeric wetting agent IPN. An existing problem relates to producing ophthalmically acceptable ophthalmic lenses, such as silicone hydrogel contact lenses, without requiring a surface treatment or a polymeric wetting agent IPN, and without requiring a contact point coupling method for contact lens molds used in the production of the lenses.
All publications, including patents, published patent applications, scientific or trade publications and the like, cited in this specification are hereby incorporated herein in their entirety.